Use of Independent Data Sets in Analyzing Tectonic Plate Boundaries
Use of the GoogleEarth (for desktop) platform, combined with kmz layers compiled by the author: the Bird (2003) digital model of plate boundaries; sea floor age based on the geomagnetic time scale; data from eight different hot spot tracks; and time series and horizontal velocity vectors from 2600+ GPS stations.
Armed with previous knowledge about basic plate tectonic theory, students hypothesize about motions across specific plate boundaries. They then test their hypotheses by using a Google Earth platform to calculate relative plate velocities (speed and direction) across these specific boundaries using three independent methods: 1) long-term average rates from sea-floor age, 2) long-term average rates from presumed hot spot tracks and 3) near real-time rates from high-precision GPS data. Focusing on relative rates across boundaries allows students to get around reference frame issues when comparing the different data sets, and they also gain experience in quantitative skills using real data. In doing so, students confirm the basic tenets of plate tectonic theory, but also discover its complexities and limitations: plate boundaries are not simply those narrow lines depicted in plate boundary models, plate velocities change over time and space, internal plate deformation does occur and "hot spots" don't work like hypodermic needles providing a constant, steady pipeline of magma. That is, students reinforce their knowledge of a fundamental theory while also grappling with areas of current research.
We use this activity in two courses - in our "Fundamentals of Solid Earth Science" for majors and engineers, and in "Natural Disasters" course for non-majors. The level of the activity is easy to adjust and serves the needs of both populations in helping students understand "how the earth works" and giving them the scientific understanding needed for assessing and mitigating plate tectonic-related risks to human populations.
Why It Works
Students come to this activity familiar with the basic assumptions of plate tectonics and nature of plate boundaries, but end up reinforcing this understanding as well as discovering complexities, by working with data on which the theory is based and experiencing the power of independent data sets. For example, a single hot spot track could be explained by 1) a moving plate and a fixed hot spot, or 2) a fixed plate and a moving hot spot. But when several hot spot tracks are examined, along with sea floor age, and GPS data - the moving plate and fixed hot spot model is the better explanation. Google Earth is an easy-to-use and excellent platform that facilitates independent exploration of multiple data sets and gives students flexibility in determining which data to use in their analyses.